From: Pekka Enberg <penberg@cs.helsinki.fi>
To: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Vegard Nossum <vegard.nossum@gmail.com>,
Ingo Molnar <mingo@elte.hu>,
linux-kernel@vger.kernel.org, Eric Paris <eparis@redhat.com>
Subject: Re: shmem_fill_super(): WARNING: kmemcheck: Caught 32-bit read from uninitialized memory
Date: Mon, 21 Sep 2009 14:07:19 +0300 [thread overview]
Message-ID: <1253531239.5216.27.camel@penberg-laptop> (raw)
In-Reply-To: <Pine.LNX.4.64.0909211126080.32504@sister.anvils>
Hi Hugh,
On Mon, 2009-09-21 at 11:49 +0100, Hugh Dickins wrote:
> I got a bit anxious when I saw that the mode arg to shmem_get_inode()
> is declared as an int: was afraid that compiler was then passing a bad
> upper half down, which in fact would cause no trouble, but how could it
> be sure of that? However, it looks okay: after doing the 32-bit load,
> it goes on to do a movzwl %ax,%eax - seems an odd way to proceed to me,
> but I bet it knows a lot more about efficiency of memory loads than I do.
Yeah, that's a common cause of kmemcheck false positives. I guess GCC
wants to avoid a partial register stall in the memory load and expects
CPU register renaming to work for "movzwl %ax, %eax" or something.
Pekka
prev parent reply other threads:[~2009-09-21 11:07 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-09-15 8:09 WARNING: kmemcheck: Caught 32-bit read from uninitialized memory (bf438284) Ingo Molnar
2009-09-15 8:59 ` Eric Dumazet
2009-09-15 9:34 ` Ingo Molnar
2009-09-15 9:39 ` David Miller
2009-09-20 7:22 ` shmem_fill_super(): WARNING: kmemcheck: Caught 32-bit read from uninitialized memory Ingo Molnar
2009-09-20 17:35 ` Vegard Nossum
2009-09-20 17:55 ` Pekka J Enberg
2009-09-20 17:58 ` Ingo Molnar
2009-09-20 18:01 ` Pekka Enberg
2009-09-20 18:40 ` Ingo Molnar
2009-09-20 18:04 ` Cyrill Gorcunov
2009-09-21 10:49 ` Hugh Dickins
2009-09-21 11:07 ` Pekka Enberg [this message]
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